The present disclosure relates to a polishing slurry, and more particularly, to a polishing slurry used for planarizing tungsten by a chemical mechanical polishing process in a semiconductor manufacturing process, and a substrate polishing method using the same.
Since the surface unevenness of each layer is transferred to a next layer, the degree of waviness of the lowermost layer becomes important, as the size of semiconductor devices gradually decrease, and the number of layers of metal wirings gradually increase. The waviness may seriously influence to such an extent that a photolithography process in a next step may become difficult. Thus, to improve the yield of semiconductor devices, for example, to easily perform a photolithography process in a semiconductor manufacturing process and to decrease the deviation of the resistance of wirings, a planarization process for removing the waviness of an uneven surface generated during performing various processes is necessary. A planarization method includes a reflowing method, an etch back method, a chemical mechanical polishing (CMP) method, etc. after forming a thin film.
A CMP process is a process of evenly polishing by contacting the surface of a semiconductor wafer to a polishing pad, performing a rotational motion and providing a slurry including an abrasive and various compounds. That is, the surface of a substrate or a layer thereon is chemically and mechanically polished by the slurry and the polishing pad and planarized. Generally, the polishing process of a metal is known to be performed by repeating a forming process of a metal oxide (MOx) by an oxidant and a removing process of the metal oxide thus obtained by an abrasive.
The polishing process of tungsten widely used as wirings of a semiconductor device also is performed by a repeating mechanism of a forming process of tungsten oxide (WO3) by an oxidant and a potential modulator and a removing process of the tungsten oxide by an abrasive. Thus, to improve polishing efficiency, the formation of the tungsten oxide by adding the oxidant and the potential modulator, and the removal of the tungsten oxide by the abrasive are necessary to be effectively performed. However, commonly used abrasive, colloidal silica, is not effective because the removal of the tungsten oxide is highly dependent on the concentration of the oxidant. In addition, in the case that the polishing is performed with respect to a substrate including patterns such as a trench, defects such as dishing or erosion are frequently generated. When the dishing or the erosion is generated, the operation properties of a device may be negatively influenced including the malfunction of the device thus manufactured. Therefore, the defects such as dishing or erosion are required to be decreased, and so, the control of chemical factor and mechanical factor are necessary.
The control of the chemical factor may include the control of slurry properties by controlling the concentration of the oxidant and the potential modulator, and the control of the mechanical factor may include the control of the change of commonly used abrasive particles. Meanwhile, Korean Patent Publication No. 10-0948814 discloses a method of polishing by two steps to decrease dishing and erosion. However, in this case, a plurality of slurries is prepared, and a plurality of processes is performed. Thus, the process becomes complicated, and productivity is deteriorated.